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Millions of tonnes of Pb-Zn ore flotation tailings and waste rock have been discharged at sites in northern Tunisia without concern for environmental issues. The tailings are dominantly fine grained (<125 μm), with high porosity and permeability. The tailings were characterized to assess base metal (Pb, Zn, and Cd) mobility. The relatively low percentage of iron sulphide and the dominance of carbonates in the matrices of the tailings indicated that only neutral mine drainage is likely. Batch sequential testing showed that the calcium and sulphate, which are the major ionic species in solution, are derived mainly from the dissolution of gypsum and not from neutralization of acidity generated by pyrite oxidation. Yet, despite the carbonate setting, the resultant neutral to slightly alkaline pH, and prolonged weathering, the studied flotation tailings maintain their capacity to release contaminants, notably Zn and Cd, into the environment. The amount of Zn that dissolves (2,400 μg L, on average), though significant, is below the background concentrations in the Mejerda River and the environmental norms established for surface waters. Pb concentrations come close to the standards, but only Cd (18 μg L, on average) sometimes exceeds current river water concentrations and environmental standards. [ABSTRACT FROM AUTHOR]

In Tunisia, it was reported that Meriones shawi, a desert rodent, was contaminated by heavy metals around several industrial sites. In the present study, the effects of cadmium (Cd) on water metabolism regulation was studied in adult male Meriones shawi that received contaminated diet with cadmium chloride (CdCl2) for 8 days at (1 g Cd/1 L H2O/1.5 kg of granule flour). Expression of arginine-vasopressin (AVP), a crucial hormone for water regulation, was studied by immunohistochemistry in the hypothalamic supraoptic nucleus and paraventricular nucleus. Inspite of variations in water intake, Meriones shawi successfully maintained a balance between water influx and efflux. Cd treatment did not modify water flux rates. Total body water volume remained constant during the treatment in all groups studied. In contrast to what is known in laboratory rodents, water restriction induced an increase in expression of AVP in both supraoptic nucleus and paraventricular nucleus after eight days and two weeks of the experiment, respectively. A similar effect was also observed by treating Meriones with Cd. However, expression of AVP immunoreactivity from deprived water animals in the presence of Cd was markedly and significantly lower than in the absence of Cd. We conclude that Cd exposure modifies the vasopressinergic neuronal system and provides information regarding the neurotoxicity risks that this element presents for mammals and human populations exposed to even low amounts of Cd, without directly affecting water metabolism. Suitability of Meriones shawi as an accumulation bioindicator for Cd was also confirmed in this study. [ABSTRACT FROM AUTHOR]

Cadmium (Cd) and metallothionein (MT) concentrations were analysed in the gills and digestive gland of clams Ruditapes decussatus collected from two sites of the Gulf of Gabès (Tunisia) which differ by their degree of pollution. The effect of biotic (maturity stages, protein, sex and body mass) and abiotic factors (temperature, salinity, site and season) on Cd and MT concentrations showed that in the reference site ¿Bordj d¿Ungha¿ physiological changes caused by gamete development and maturity contributed more to changes in MT concentrations than the bioavailable Cd concentrations; whereas, in the contaminated site ¿El Hofra¿, MT induction responded to raised Cd bioavailabilities rather than to physiological changes. With a view to using MTs as metal exposure biomarker in monitoring program, our results show that the analysis in the digestive gland seem to be more relevant than in gills, and that males appear as the most promising candidates compared to females in the determination of this biomarker. [Copyright &y& Elsevier]